Condenser type terminal devices employing unit insulating cylinders

ABSTRACT

A CONDENSER-TYPE TERMINAL DEVICE COMPRISING A PLURALITY OF UNIT INSULATING CYLINDERS ENCLOSING A CENTER CONDUCTOR AND BEING FIXED THERETO, SAID UNIT INSULATING CYLINDERS BEING OPPOSED TO EACH OTHER ACROSS A CLEARANCE INTERSECTING THE AXIS OF THE CENTER CONDUCTOR AT A PREDETERMINED OBLIQUE ANGLE, AND, FURTHER, EQUIPOTENTIAL ELECTRODES IN THE UNIT INSULATING   CYLINDERS OPPOSED TO EACH OTHER WITH A CLEARANCE THEREBETWEEN BEING ARRANGED IN STAGGERED RELATION.

United States Patent Inventors Toklo lsogai;

Takasbi Tahara; Toshio Inoue, Hitachi-shi, Japan Appl. No. 881,960

Filed Dec. 4, 1969 Patented June 28, 1971 Assignee Hitachi, Ltd.

Tokyo, Japan Priority Dec. 11 1968 Japan 43/90,241

CON DENSER-TYPE TERMINAL DEVICES EMPLOYING UNIT INSULATING CYLINDERS 11 Claims, 8 Drawing Figs.

US Cl 174/143, 174/31, 174/73 Int. Cl 1101b 17/28 Field otSeareh 174/31,?3, 143

[56] References Cited UNITED STATES PATENTS RE26,066 7/1966 Huston 174/143X 984,129 2/1911 Fortescue.... 174/143 2,852,596 9/1958 Prince 174/73 FOREIGN PATENTS 1.559,]15 1/1969 France 174/73 431,367 7/1926 Germany 174/31 339,677 12/1930 Great Britain.. 174/31 478,839 3/1953 Italy 174/143 194,151 2/1965 Sweden 174/143 Primary Examiner- Laramie E. Askin Attorney-Craig, Antonelli, Stewart and Hill ABSTRACT: A condenser-type terminal device comprising a plurality of unit insulating cylinders enclosing a center conductor and being fixed thereto, said unit insulating cylinders being opposed to each other across a clearance intersecting the axis of the center conductor at a predetermined oblique angle, and, further, equipotential electrodes in the unit insulating cylinders opposed to each other with a clearance therebetween being arranged in staggered relation.

PATENTEDJUu28l9fl 3588319 SHEET 2 OF 3 H63 FIG. 4

INVENTORS TIIKIO ISOGAI, TAKASHI TAMARA a d TOSHIO INOME.

BY W 4104 4 M ATTORNEYS PATENIEO 41m 28 1971 3588.319 SHEET 30F 3 INVENTORS TOKIO Isms-AI, rAKASHI TAHARA and TOSHIO INOLAF.

ATTORNEYS CONDENSER-TYPI'J-TERMINAL DEVICES EMPLOYING UNIT INSULATING CYLINDERS BACKGROUND OF THE INVENTION The present invention relates to a condenser-type terminal device.

DESCRIPTION OF THE PRIOR ART Recent development in the ultrahigh voltage power transmission technique has been so remarkable that a power transmission system of the order of 500 kv. has come to be put into practical use. Accordingly, electric power equipment and apparatus such as transformers will tend to be larger and larger in size and capacity in the future and the increasing capacity will result in the increased dimensions thus accelerating the tendency toward the heavier equipment and apparatus.

Naturally, condenser-type terminal devices such as bushings and the like which are used with these equipment and apparatus will inevitably tend to be larger in size, thereby furthering the aforesaid trend toward the larger and heavier equipment and apparatus. However, since the larger and heavier equipment and apparatus are objectionable from various aspects such as materials and manufacturing equipment and techniques, it will be significant to contemplate the provision of smaller and more compact condenser-type terminal devices as far as possible.

The condenser-type terminal device such as a condenser bushing for use with high-voltage apparatus comprises a center conductor with a given current carrying capacity, an insulating cylinder surrounding the center conductor and securely mounted thereon, a plurality of electrode layers disposed in the insulating cylinder substantially concentrical with the center conductor to equally bear part of the voltage by their respective electrostatic capacities, and a mounting flange secured to the surface of the insulating cylinder for mounting on the oil tank wall and the like of ground potential.

Since the length of insulating cylinders for condenser-type terminal devices will become longer substantially in proportion to the magnitude of working voltages, the length of those which are used on the ultrahigh voltages will naturally exceed meters. In the past, however, insulating cylinders have been subject to various restrictions imposed by the layers of electrode disposed in the insulating cylinders, the width of insulating paper used as the insulating material and the dimensions of various manufacturing equipment such as resin impregnating apparatus, and thus their manufacture was not an easy matter and, even if they were manufactured, they could not be produced economically. Such being the case, the high-voltage condenser-type terminal devices have hitherto been made by securely mounting successively a plurality of unit insulating cylinders on a center conductor, instead of mounting on the center conductor a long insulating cylinder comprising layers of electrode formed therein.

In other words, each of the plurality of unit insulating cylinders with layers of electrode disposed therein were previously formed, for example, in the resin potting or encapsulating process and the preformed insulating cylinders were then securely mounted successively on the center conductor to enclose the latter, or the respective unit insulating cylinders were successively wound directly around the center conductor, and when insulating material such as oil or the like was filled into a clearance formed between the respective unit insulating cylinders to provide a thus completed device with the equal electrical and mechanical properties as the condenser-type terminal device comprising a single and long insulating cylinder mounted on the center conductor. If necessary in practical use, the insulating cylinders were surrounded with porcelain tubes or insulators which were then filled with oil or the like.

However, in the condenser-type terminal devices composed of a plurality of unit insulating cylinders mounted on a center conductor as described above, its withstand voltage would largely depend upon the withstand voltage stability of the clearance between the unit insulating cylinders. It has been shown that, for example, as the breakdown voltage of the insulating material such as oil or the like filled into the clearance between the opposed unit insulating cylinders would be of the order of 60 kv./cm. and very low as compared with the breakdown voltage of to kv./cm. for the plastic insulations of the unit insulating cylinders, even if the stray capacitance due to the electrodes of the adjacent unit insulating cylinders were taken into consideration to provide the equal electrostatic capacity between the adjacent electrodes in the respective unit insulating cylinders so that the respective cylinders would bear the equal share of the voltage, while the respective equipotential electrodes in the opposing unit insulating cylinders across the clearance were placed at equal distances from the center conductor so that the equipotential surface in the clearance would be parallel to the axial direction of the center conductor, the creepage breakdown voltage at the clearance portion would not depend on the creeping distances of the unit insulating cylinders facing the clearance, but it would largely be determined by the distance between the innermost layer and outermost layer electrodes of the plurality of electrodes disposed in the unit insulating cylinders or the integrated distances which are normal to the equipotential surface.

Accordingly, in order to considerably improve the creepage withstand voltage of the clearance, it is preferable to arrange in a way such that the equipotential surfaces of the respective electrodes in the unit insulating cylinder intersect the clearance practically at right angles to thereby increase the integrated distance normal to the equipotential surfaces, or alternately, if the equipotential surfaces are generally parallel with the axis of the center conductor, it is desirable to increase the interelectrode distance between the innermost layer and outermost layer electrodes in the unit insulating cylinder to thereby substantially increase the creeping distance.

However, the latter attempt wherein a larger interelectrode distance is provided between the innermost layer and outermost layer electrodes in the respective unit insulating cylinders has drawbacks that, as compared with the conventional condenser-type terminal devices, the device according to this attempt tends to be larger and heavier and it cannot be economically manufactured, thus failing to attain the miniaturization of the device which is the characteristic of the condenser-type terminal devices.

SUMMARY OF THE INVENTION An object of the present invention is therefore to make it possible to easily manufacture a condenser-type terminal device, more particularly a high-voltage condenser-type terminal device comprising a center conductor, a plurality of unit insulating cylinders securely mounted on said center conductor to enclose said conductor, each of said insulating cylinders having formed therein plural layers of electrode disposed substantially concentrical with said center conductor, and a mounting flange securely fixed to the unit insulating cylinders.

Another object of the present invention is to provide a condenser-type terminal device which is smaller and can be economically manufactured as compared with the conventional devices of this type.

A still further object of the present invention is to provide a condenser-type terminal device wherein a plurality of unit insulating cylinders securely fixed to a center conductor to enclose said conductor are opposed to each other across a clearance crossing the axis of the center conductor at a predetermined oblique angle, and the equipotential surfaces of electrodes intersect said clearance substantially at right angles, whereby the improvements in electrical properties such as dielectric breakdown strength and corona discharge are attained by the clearance defined by opposing unit insulating cylinders.

The above and other objects and features of the present invention will be apparent from the following descriptions of the respective embodiments of the present invention.

The present invention is characterized by a condenser-type terminal device comprising a center conductor, a plurality of unit insulating cylinders securely fixed to the center conductor to enclose said conductor, the unit insulating cylinders being opposed to each other across a clearance crossing the axis of the center conductor at a predetermined oblique angle, plural layers of electrodes formed in the respective unit insulating cylinders substantially concentric with the center conductor, means for providing the electrodes in the unit insulating cylinders opposed across the clearance with electrical potentials such that the equipotential electrodes in one of the unit insulating cylinders whose opposing face forms an acute crossing angle with the axis of the center conductor are placed toward the center conductor nearer than the equipotential electrodes in the other unit insulating cylinder and a mounting flange securely fixed to the outer surface of the unit insulating cylinders.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partially sectional front view showing an example of the condenser-type terminal device of the present invention which is covered by a porcelain tube or insulator, wherein the center conductor is enclosed by two unit insulating cylinders fixed thereto and opposed to each other with a clearance defined therebetween, the clearance crossing the axis of the center conductor at a predetermined oblique angle;

FIG. 2, FIG. 3 and FIG. 4 are partially sectional front views of different types of the condenser-type terminal device according to the present invention with their porcelain tube being removed, FIG. 2 showing an example wherein two unit insulating cylinders are securely fixed to a center conductor to enclose the latter as is the case with FIG. I, but its clearance crosses the axis of the center conductor at a predetermined oblique angle different from that of FIG. 1 and one of the unit insulating cylinders is provided with two groups of electrodes each comprising plural layers of the electrodes in juxtaposition to the axis of the center conductor, FIG. 3 showing another example comprising two unit insulating cylinders in the first stratum and one in the second stratum with the respective unit insulating cylinders being securely fixed to the center conductor to enclose the latter, and FIG. 4 showing still another example wherein unit insulating cylinders securely fixed to a center conductor to enclose the latter comprise three cylinders in the first stratum, two in the second stratum and one in the outermost stratum;

FIG. 5 and FIG. 6 are enlarged views respectively showing the equipotential electrodes in the unit insulating cylinders opposed to each other across a clearance crossing the axis of the center conductor at a predetermined oblique angle;

FIG. 7 is a graph showing the relationship between an angle 0 formed by the surface of the clearance crossing the axis of the center conductor at a predetermined oblique angle and the equipotential surfaces intersecting the clearance, and the corona discharge voltage E; and

FIG. 8 is a longitudinal sectional view showing an example of another condenser-type terminal device wherein unit insulating cylinders are securely fixed to two center conductors joined together by connecting means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, a condenser-type terminal device 10 comprises a center conductor 11 centrally extending in the axial direction'and having a given current carrying capacity and moreover two unit insulating cylinders 12 and 13 enclose the center conductor 11 and are securely fixed thereto. The unit insulating cylinders 12 and 13 are mounted on the center conductor 11 to oppose each other across a small clearance 14 which crosses the axis of the center conductor 11 at a predetermined oblique angle. The clearance 14 is then filled with insulating material such as degassed oil (not shown) to reduce the generation of corona. The unit insulating cylinders 12 and 13 are provided with plural layers of electrodes 15 and l6 composed of metal foils, for instance, and disposed substantially concentrical with the center conductor 1 I. Securely fixed to the outer surfaces of the unit insulating cylinders is a mounting flange 17 for mounting the condenser-type terminal device 10 onto the oil tank wall or the like of an apparatus, and the unit insulating cylinder 12 is enclosed by a porcelain tube or insulator 18 which is filled with oil 19 and provided with an upper chamber 20 on the upper end thereof to compensate for the expansion and shrinkage of the oil 19.

The aforesaid porcelain tube 18, the oil 19 filled within the tube 18 and the upper chamber 20 disposed on the upper end of the tube 18 are not essential in the condenser-type terminal device according to the present invention, therefore, they are not specifically mentioned in the description of embodiments other than that of FIG. 1. The plurality of electrodes 15 and 16 in the unit insulating cylinders 12 and 13 facing each other across the clearance 14 have the properly determined potentials. In FIG. 1, the innermost layer electrodes are made equipotential with the center conductor 11 by potential imparting means 21 and 22 such as lead wires and the outermost layer electrodes are rendered to be of the same potential as the mounting flange 17 by potential imparting means 23 and 24 such as lead wires, whereby the equipotential electrodes in the unit insulating cylinders 12 and 13 positioned on opposite sides of the clearance 14 are so arranged that the unit insulating cylinder 13 placed on one side of the clearance, where the crossing angle between its opposing face and the axis of the center conductor 11 forms an acute angle, contains its equipotential electrodes 16 positioned nearer the center conductor 11 than the respective equipotential electrodes 15 in the other unit insulating cylinder 12, with a result that the equipotential surfaces intersect the clearance 14 of a predetermined oblique angle at a preset angle. This, in turn, increases the integrated distance normal to the equipotential surfaces which determine the creepage breakdown voltage at the clearance 14, hence the distance between the innermost layer electrode and the outermost layer electrode in the respective unit insulating cylinders is equivalently increased so that a terminal device may be obtained which has electrical properties such as the corona discharge voltage and breakdown voltage similar to those of the larger and heavier condenser-type terminal devices. The foregoing will be more apparent from the following descriptions.

If the respective equipotential electrodes 15 and 16 are disposed in the unit insulating cylinders 12 and 13 on opposite sides of the clearance 14 so that the unit insulating cylinder 13 placed on one side of the clearance, where the crossing angle between the clearance 14 and the axis of the center conductor 11 is an acute angle, contains its equipotential electrodes 16 positioned nearer the center conductor 11 than those in the other unit insulating cylinder, the equipotential surfaces, which extend between the respective equipotential electrodes, and the clearance 14 intersect each other at an angle 0. As stated above, the creepage breakdown voltage at the clearance 14 depends on the integrated distance normal to the equipotential surface intersecting the clearance 14, so it will be understood that, when a unit insulating cylinder has n layers of electrode and 1. represents the distance between given electrodes normal to the equipotential surface, the integrated distance is given by Ln sin 6. In this case, if 0 is 11/2, the maximum integrated distance normal to the equipotential surfaces for each unit insulating cylinder may be obtained.

FIG. 5 shows an instance where the crossing angle 0 between the clearance 14 and the equipotential surface is given by 1r/2, while FIG. 6 shows another instance where the angle 0 is smaller than 1r/2, and it will be evident that, in FIG. 6, the distance 1 between the electrodes normal to the equipotential surfaces is naturally shorter than the case that the crossing angle is 1r/2. FIG. 7 shows the relationship between the crossing angle 0 made by the intersection of the equipotential surfaces with the clearance and the corona discharge voltage E which has an important effect on the breakdown voltage of condenser-type terminal devices, and it is desirable to use insulating cylinders within the hatched region in the graph, because the corona discharge voltage E will be maximum when the crossing angle 6 is 11/2, namely, the clearance and the equipotential surfaces cross each other at right angles, and the corona discharge voltage decreases when the angle 0 is either smaller or larger than 1r/2. Accordingly, by making the clearance and the equipotential surfaces cross each other substantially at right angles, it is possible to raise the breakdown voltage of condenser-type terminal devices and to manufacture them easily and economically.

With the condenser-type terminal device 10 according to the present invention shown in FIG. 1, in enclosing the center conductor 11 with the unit insulating cylinders 12 and 13 and securely fixing the latter to the former, the cylinders 12 and 13 may be opposed to each other across the clearance 14 which crosses the axis of the center conductor 11 at a predetermined oblique angle, further, the equipotential electrodes in the unit insulating cylinder 13 located on one side of the clearance where the crossing angle between the center conductor 11 and the clearance becomes an acute angle, may be positioned nearer the center conductor 11 than those in the other unit insulating cylinder 12 tothereby make the clearance 14 and the equipotential surfaces intersect each other substantially at right angles. Thus, the objects of the present invention may be attained satisfactorily.

Referring now to FIG. 2, a condenser-type terminal device 30 comprises, as is the case with the one shown in FIG. 1, a center conductor 31 having a given current carrying capacity, two unit insulating cylinders 32 and 33 which encloses and are fixed to the center conductor in opposed relation with each other across a clearance 34, and a mounting flange 37 securely fixed onto some portions of the outer surfaces of the unit insulating cylinders 32 and 33. However, the clearance 34 across which the two unit insulating cylinders 32 and 33 face each other makes an oblique angle different from that of FIG. 1 between itself and the axis of the center conductor 31. Accordingly, while the unit insulating cylinder 33 contains only one group of plural layers of electrodes 36 disposed substantially concentric with the center conductor 31, the other unit insulating cylinder 32 located on the opposite side of the clearance 34 contains two groups of plural layers of electrodes 35a and 35b which are disposed in juxtaposition with respect to the axis of the center conductor 31.

Since the unit insulating cylinder 32 is located on one side of the clearance 34, where the oblique angle of the clearance 34 which intersects the axis of the center conductor 31 is an acute angle, as compared with the plural layers of electrodes 36 in the unit insulating cylinder 33 opposed thereto interposing the clearance 34, the electrodes 35b in one of the two groups are disposed so that the corresponding equipotential electrodes are placed nearer to the center conductor 31, whereby, as explained in conjunction with FIG. 1, the clearance 34 and the equipotential surfaces intersect each other substantially at right angles. Thus, the objects of the present invention can be attained. On the other hand, the plural layers of electrodes 35a in the other group are disposed in order to improve the potential distribution on the surface of one end of the unit insulating cylinder 32 reverse to its end facing the clearance 34. Consequently, the group of plural layers of electrodes 35a, which does not face the clearance 34, are placed farther than the group of plural layers of electrodes 35b with respect to the center conductor 31. Of the plural layers of electrodes 35a and 35b in the respective groups, the innermost layer electrodes and the outermost layer electrodes are respectively interconnected equipotentially by connecting means 38 and 39 such as lead wires to thereby determine the potential of the respective layers. Further, the interconnection between the center conductor and the innermost layer ones of the electrodes 35a, 35b and 36 in the unit insulating cylinders 32 and 33, and the interconnection between the outermost layer ones thereof and the mounting flange 37 are respectively provided to maintain equipotentially by means of potential im parting means 40, 41, 42 and 43 such as lead wires so as to attain the aforesaid effects.

As already stated in the description of FIG. 1, the clearance 34 is filled with insulating material such as degassed oil to further improve the withstand voltage of this portion. Such insulating material should preferably be filled through the vacuum injection process or the like to completely eliminate the void which may cause the corona discharge within the clearance 34.

In FIG. 3, a condenser-type terminal device 50 is adapted for use with higher voltages than the devices shown in FIGS. 1 and 2, and it comprises, as is the 'case with the device shown in FIG. 2, a center conductor 31, two unit insulating cylinders 32 and 33 in the first stratum which enclose and are securely fixed to said conductor 31 opposing to each other interposing a clearance 34 therebetween, a unit insulating cylinder 51 of the second stratum securely mounted 'over the first-stratum cylinders, and a mounting flange 37 securely fixed to the outer surface of the unit insulating cylinder 51. Of course, the second-stratum unit insulating cylinder 51 has plural layers of electrodes 52 disposed concentrically with the center conductor 31; These unit insulating cylinders 32, 33 and 51 in the first and second strata bear their respective burdens of the high voltages by virtue of the electrostatic capacities of the electrodes 35a, 35b, 36 and 52. Of the electrodes in the secondstratum unit insulating cylinder 51,-the innermost layer electrode is equipotentially connected with the outermost layer electrodes in the unit insulating cylinders 32 and 33 in the first stratum respectively, and the outermost layer electrode with the mounting flange 37 by means of the respective potential imparting means 53,54 and 55 such as lead wires.

A condenser-type terminal device 60 shown in FIG. 4 is adapted for use on the still higher voltages than the abovedescribed devices shown in FIGS. 1 to 3, and it comprises a center conductor 61, six unit insulating cylinders 62 to 67 in three strata which enclose and are securely fixed to the center conductor 61, and a mounting flange 68 securely fixed to the outer surface of the outermost-stratum unit insulating cylinder 67.

The three unit insulating cylinders 62, 63 and 64 in the first stratum and the two unit insulating cylinders 65 and 66 in the second stratum are mounted so that they are respectively opposed to one another across clearances 69, 70 and 71 which intersect the axis of the center conductor 61 at preset oblique angles and are filled with an insulating material respectively.

Among the six unit insulating cylinders, the four unit insulating cylinders 62 to 65 are respectively provided with two groups of plural layers of electrodes 72a, 72b, 75a and 75b which are disposed substantially concentric with the center conductor 61 and in juxtaposition with the axis of the center conductor 61, while the remaining two unit insulating cylinders 66 and 67 are respectively provided with one group comprising plural layers of electrodes 76 or 77 which are disposed substantially concentrical with the center conductor 61. Of the two groups of the electrodes disposed in each one of the unit insulating cylinders 62 to 65, the innermost layer electrodes and the outermost layer electrodes are equipotentially interconnected respectively, as previously described, by means of connecting means such as lead wires, which are not designated by any numerals in the FIGS. to thereby determine the potentials of the individual electrodes.

Among the respective plural layers of electrodes 72a, 72b,

..... 77 in the unit insulating cylinders 62 to 67 of in first,

second and third strata, the innermost layer electrodes and the outermost layer electrodes are, as described in conjunction with FIG. 3, made equipotential with the center conductor 61, the mounting flange 68, or the outermost layer electrodes or the innermost layer electrodes of the adjacent electrodes by potential imparting means such as lead wires which are not designated by any numerals in the FIG., thereby determining the potential of the respective electrodes and simultaneously protecting those portions, where the unit insulating cylinders are mounted, from being electrically weakened.

As already mentioned in conjunction with FIGS. 1, 2 and 3, the respective plural layers of electrodes in the unit insulating cylinders 62 through 66 opposed to one another across the clearances 69, 70 and 71 which intersect the axis of the center conductor 61 at predetermined angles are so arranged that, of the equipotential electrodes 72b through 76, those disposed in the unit insulating cylinders which are located on such sides of the clearances 69, 70 and 71, where the crossing angles made by the clearances and the axis of the center conductors 61 are acute angles, are positioned nearer the center conductor 61 than the electrodes in the opposite insulating cylinders, whereby the respective clearances and the equipotential surfaces intersect each other substantially at right angles, thus making it possible to satisfactorily attain the objects of the present invention.

The juxtaposed two groups of plural layers of electrodes 72a, 72b, 75a and 75b in the unit insulating cylinders 62 through 65 may be, as will be seen from the HO, positioned at equal distances from the center conductor 61 as shown in some unit insulating cylinders, or they may be placed in dif ferent positions as shown in other unit insulating cylinders, and these two groups of plural layers of electrodes are dif ferently disposed so that the respective clearances and thc equipotential surfaces may intersect each other substantially at right angles. Evenif more than two groups of such plural layers of electrodes are included in a unit insulating cylinder, there may be no trouble, provided that the aforesaid relation is established between one unit insulating cylinder and the other one opposed to each other across a clearance.

Although some constructions of the condenser-type terminal device have been illustrated by way of examples wherein a plurality of unit insulating cylinders, two unit insulating cylinders in the embodiments of FIGS. 1 and 2, three cylinders in two stratain the case of FIG. 3, and six cylinders in three strata in the construction of FIG. 4, are securely mounted onto a center conductor enclosing the latter, there is no particular limitation in the present invention with respect to the number of the strata and the number of the unit insulating cylinders. Thus, what is essential is to arrange unit insulating cylinders on opposite sides of clearances which intersect the center conductor at predetermined oblique angles and further to make the respective clearances and the equipotential surfaces intersect each other substantially at right angles so that the objects of the present invention may be satisfactorily attained.

The number of the strata and the number of unit insulating cylinders will be determined by the dimensions of condensertype terminal devices which in turn depend on the working voltages, the manufacturing equipment, etc., although there may be a eertainlimit because the complexity in manufacturing will be caused by an excessively large number thereof and will prevent satisfactory attainment of the objects of the present invention.

Referring to FIG. 8, a condenser-type terminal device 80 is shown which is employed in an application wherein electrical connection is provided by means of connecting means 83 such as a tulip-type connector between a center conductor 81 in an apparatus such as a transformer in a gassed power installation, where the conductor is covered with a casing 84a which is filled with an insulating gas, and another center conductor 82 of another apparatus such as a circuit breaker, where the conductor 82 is covered with a casing 84b which is also filled with an insulating gas.

The center conductors 81 and 82 are provided with unit insulating cylinders 85 and 86 which enclose and are securely fixed to these conductors respectively and mounting flanges 87 and 88 which are securely fixed onto the outer surfaces ofv the cylinders 85 and 86 respectively. The mounting flanges 87 and 88 are then mounted on the casings 84a and 84b which enclose the center conductors 81 and 82 so that the unit insulating cylinders 85 and 86 may serve as supporting members for these center conductors. The unit insulating cylinders 85 and 86 are opposed to each other across a clearance 89 which, at a predetermined oblique angle, intersects the axis of the center conductors 81 and 82 which has been interconnected by the connecting means 83, and further, plural layers of electrodes 90 and 91 are disposed in the respective cylinders substantially concentric with the center conductors 81 and 82.

Of the plural layers of electrodes 90 and 91, the innermost layer electrodes and the outermost layer electrodes are equipotentially connected with the center conductors 81 and 82 and the mounting flanges 87 and 88, respectively, by means of connecting means 92 to 95 such as lead wires to thereby determine the potentials of the respective electrodes. In the unit insulating cylinder 86 on one side of the clearance, where the angle made by the center conductors 81 and 82 and the clearance is an acute angle, the electrodes 91 are so disposed that they are disposed nearer the center conductor 82 than the corresponding equipotential electrodes in the other unit insulating cylinder 85 located on the other side of the clearance, whereby the clearance 89 and the intersecting equipotential surfaces cross each other substantially at right angles, thus, the creeping breakdown at the clearance is prevented to thereby attain the objects of the present invention.

The portion of the device where the unit insulating cylinders 85 and 86 are opposed to each other across the clearance 89 is enclosed with an intermediate connection casing 96 to provide a connection between the mounting flanges 87 and 88 and also to protect this portion from contamination. This intermediate connection casing 96 is then filled with an insulating material such as oil or insulating gas of the same kind as employed in the casings 84a and 84b to further improve the electrical properties of the device at the clearance 89. In case that it is necessary to take off the connection between the associated apparatuses, to remove the intermediate connection casing and to move the center conductors 81 and 82 interconnected by the connecting means 83 relatively to each other, the unit insulating cylinders 85 and 86 mounted on the conductors and facing each other across the clearance 89 will be exposed to air and moreover the clearance 89 will be made wider due to the relative movement of the conductors, as a result, the clearance 89 and the equipotential surfaces may not cross each other at right angles. However, if it is so arranged previously that the connection and disconnection of the conductors may be effected to remain within the region shown by a hatched portion in FIG. 7, the creeping breakdown at the clearance 89 may be avoided, therefore, there will be no need to increase the dimensions of the condenser-type terminal device. 7

As previously mentioned, the unit insulating units 85 and 86 mounted on the center conductors 81 and 82 may include two or more groups of electrodes, provided that this does not prevent the clearance 89 and the equipotential surfaces from intersecting each other substantially at right angles. Moreover, if one of the unit insulating cylinders tends to be rather large, it may be substituted by a plurality of smaller unit insulating cylinders which are opposed to one another across the respective clearances to maintain the previously described arrangements.

The unit insulating cylinders which have been employed in the above-described embodiments of the condenser-type terminal device according to the present invention and which enclose and are securely fixed to the center conductor or conductors may be manufactured by various methods. For example, the objects of the present invention may be most satisfactorily attained if these unit insulating cylinders are preformed by alternately winding a plurality of layers of electrodes and insulating papers and the assembly is encapsulated with epoxy resin, for example.

We claim:

1. A condenser-type terminal device comprising:

a. a center conductor having a predetermined current carrying capacity;

b. a plurality of unit insulating cylinders enclosing said center conductor and being securely fixed thereto,

b. said unit insulating cylinders being opposed to each other intcrposing a clearance therebetween, said clearance intersecting the axis of said center conductor at a predetermined oblique angle;

c. plural layers of electrodes disposed in each of said unit insulating cylinders substantially concentric with said center conductor;

d. means for providing said electrodes with predetermined potentials, whereby the equipotential electrodes in said unit insulating cylinders which are opposed to each other across said clearance are so arranged that the equipotential electrodes in said one unit insulating cylinder, whose opposing face makes an acute crossing angle between itself and the axis of said center conductor are positioned nearer said center conductor than the corresponding equipotential electrodes in the other unit insulating cylinders; and

e. a mounting flange securely fixed to the outer surfaces of said unit insulating cylinders.

2. A condenser-type terminal device as claimed in claim 1,

wherein said clearance is filled with an insulating material.

3. A condenser-type terminal device as claimed in claim 1, wherein the equipotential electrodes in said unit insulating cylinders, which are opposed to each other across said clearance, are so arranged that the equipotential surfaces extending between said corresponding equipotential electrodes meet substantially at right angles with said clearance.

4. A condenser-type terminal device as claimed in claim 1, further including connecting means for connecting the innermost layer electrodes in said unit insulating cylinders to said center conductor and the outermost layer electrodes in said unit insulating cylinders to said mounting flange.

5. A condenser-type terminal device as claimed in claim 1, wherein at least one of said plurality of unit insulating cylinders is provided with at least two groups of plural layers of electrodes disposed in juxtaposition with the axis of said center conductor, and means are provided for connecting equipotentially between the innermost layer electrodes in said groups and between the outermost layer electrodes in said groups.

6. A condenser-type terminal device comprising:

a. a center conductor having a predetermined current carrying capacity;

b. a plurality of first-stratum unit insulating cylinders enclosing said center conductor and being securely fixed thereto;

b. said unit insulating cylinders being opposed to each other interposing a clearance therebetween, said clearance intersecting the axis of said center conductor at a predetermined oblique angle;

c. at least one stratum of unit insulating cylinder securely mounted on the outside of said plurality of first-stratum unit insulating cylinders to enclose said first-stratum cylinders;

d. plural layers of electrodes disposed in each of said unit insulating cylinders substantially concentric with said center conductor;

e. means for providing said electrodes with predetermined potentials, whereby the equipotential electrodes in said unit insulating cylinders being opposed to each other across said clearance are disposed so that the equipotential electrodes in one of said unit insulating cylinders, whose opposing surface and the axis of said center conductor make an acute crossing angle, are positioned nearer said center conductor than the corresponding equipotential electrodes in the other unit insulating cylinder; and f. a mounting flange fixed to the outer surface of said outermost-stratum unit insulating cylinder. 5 7. A condenser-type terminal device as claimed in claim 6, further including connecting means for providing connection between the innermost layer electrodes in said first-stratum unit insulating cylinders and said center conductor, between the outermost layer electrodes in said first-stratum unit insulating cylinders and the innermost layer electrodes in the second-stratum unit insulating cylinders, and between the outermost layer electrode in the outermost-stratum unit insulatin%cylinder and the mounting flange.

. A condenser-type terminal device comprising:

a. two center conductors each having a predetermined current carrying capacity;

b. connecting means for connecting said two center conductors with each other;

e. at least two unit insulating cylinders enclosing said center conductors and being securely fixed thereto;

. said unit insulating cylinders being opposed to each other interposing a clearance therebetween, said clearance intersecting the axis of said center conductors at a predetermined oblique angle;

d. plural layers of electrodes disposed in each of said unit insulating cylinders substantially concentric with said center conductors;

e. means for providing said electrodes with predetermined potentials, whereby the equipotential electrodes in said unit insulating cylinders being opposed to each other across said across said clearance are disposed so that the equipotential electrodes in one of said unit insulating cylinders, whose opposing surface and the axis of said center conductors make an acute crossing angle, are positioned nearer said center conductors than the corresponding equipotential electrodes in the other unit insulating cylinder;

f. a mounting flange securely fixed to the outer surface of each of said unit insulating cylinders;

g. a casing connected with each of said mounting flanges and enclosing said center conductors and each of said unit insulating cylinders; and

h. an intermediate connection casing providing a connecting member between said mounting flanges and enclosing said unit insulating cylinders and said clearance across which said unit insulating cylinders face each other.

9. A condenser-type terminal device as claimed in claim 8, wherein the center conductors provided with said unit insulating cylinders can be moved relative to each other so that said center conductors are detachable from said connecting means.

10. A condenser-type terminal device as claimed in claim 8, wherein said intermediate connection casing is filled with an insulating material.

11. A condenser-type terminal device as claimed in claim 8, further including connecting means for connecting the innermost layer electrodes in said unit insulating cylinders to the respective center conductors and the outermost layer electrodes in said unit insulating cylinders to the respective mounting flanges. 

